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This paper presents a new self-clinching fastener to connect two sheets (or plates), made from similar or dissimilar materials, placed over one another by means of a mechanical form-closed joint that is hidden inside the sheets. The development of the fastener, the definition of its main design variables and the identification of its workability limits are carried out by means of a combined experimental and numerical simulation work based on finite elements. It is shown that self-clinching by pressing the two overlapped sheets against each other to displace material around the annular groove of the fastener shank and create undercuts in both sheets requires an appropriate choice of the design variables. Wrong values of the design variables resulting in lack or excess of material displaced by plastic flow gives rise to inappropriate lap joints that cannot be used in production. The new proposed fastener allows, for the first time ever, joining by forming with the use of auxiliary elements that are harder than the sheet materials to fabricate invisible joints with no material protrusions in applications requiring minimum installation space. [ABSTRACT FROM AUTHOR]

With tremendous weight saving potential, magnesium alloy high pressure die casting components have been widely used for automotive applications. Magnesium fastening technology is thus becoming increasingly important to design engineers. Joining as-cast holes of magnesium high pressure die casting components with thread forming fasteners provides significant advantages for the assembly process, overall cost benefit and joint integrity. This type of joint is thus preferred for structural applications. Designing the thread forming fasteners with as-cast holes follows the general rules for designing for the machined holes, including carefully designing the variables such as the assembly torque range, the length of thread engagement, the hole diameter and required failure mode. In addition, special attention needs to be paid to the draft angles of the magnesium cast components that are required for the die casting process. In this paper, the effects of above key factors, individually and combined, on the joint performance of thread forming fasteners with as-cast blind holes of AM60B magnesium components are studied. A joint design philosophy was proposed to optimize both joint performance (the prevailing torque, the failure torque and the failure mode) and manufacturing easiness (the hole diameter and corresponding draft angle). The detailed design considerations for as-cast holes of magnesium HPDC are discussed and explained through a hypothetical example. [ABSTRACT FROM AUTHOR]

Roof wind design consist of three parts: determination of wind loads, evaluation of wind uplift resistance and correlating the resistance with the design load such that the resistance is higher than the load requirement. Wind uplift resistance of a system with its respective components is evaluated in laboratory testing. This paper presents a novel approach to estimate wind uplift resistance when components are substituted during field application. Wind dynamics, on a mechanically attached single-ply roofing assembly, lift the membrane and cause fluttering, introducing stresses at the attachment locations. In such assemblies, the fastener–deck interface is a critical design factor. First, by taking steel deck as a component this paper systematically characterizes the various steel decks that are commonly used in low slope application. Second component, namely the fasteners and its engagement strength with deck have been quantified for variations of its design, size and sources. Based on this component characterization, fastener pullout resistance (FPR) is identified as a verification factor for system wind resistance estimation. When variations occur in the fastener–deck interface between the proposed and the existing configurations, the present research through case studies has proved that: “as long as the FPR of the proposed configuration is higher than the existing configuration then wind uplift ratings can be maintained”. This is valid as long as both the configurations have all the remaining roofing components similar with comparable layout. Based on this verification, the study recommends that the testing lab should report the FPR along with the wind uplift resistance such that FPR can be used as a verification factor to accept design/field alternatives. [Copyright &y& Elsevier]

This paper evaluates the effect that uncertainties in measurements of time, weight, and surface area have on the determination of the corrosion rate of metal fasteners in contact with wood. Three different types of nails were driven into alkaline copper quaternary (ACQ)-treated wood and exposed to 26.7°C (80°C) at 100 % relative humidity environment for up to 1 year. It was observed that uncertainties in measurement of corrosion rate of less than 5 % could be obtained in 6 months of testing. This paper gives a description of the methods used as well as recommendations for future corrosion exposure tests in wood. [ABSTRACT FROM AUTHOR]

The use of a running clamping technology enables clamping with a welding robot during laser welding in the body-in-white shop. Unlike common clamping fixtures, clamping is operated force-controlled. In this paper a FE-simulation method of the clamping process with the running clamping technology is presented. The method is applied to a clamping experiment with aluminum L-specimens. Objective of this simulation method is the prediction of the clamping force required to close the gap between sheet metal part flanges. A closed gap between flanges is necessary to achieve a proper weld seam. Furthermore, stresses and strains as well as potential plastic strains emerging during the clamping process can be identified using FE-simulation. In this contribution the simulation method is described in detail including assumptions and simplifications, due to the transfer from real experiment to virtual model, as well as important parameters of contact modeling. Comparison of simulation results to experimental investigations shows a reasonable correspondence. [ABSTRACT FROM AUTHOR]

Fatigue is one of the most common failure modes of structures and components. The prediction of fatigue crack propagation in real structures must take into account realistic boundary conditions. The purpose of this paper is to describe a technique for modelling fasteners through FEM global structure modelling and using the model for stress state analyses and crack growth prediction. The consideration of fastener stiffness during stress analysis is an integral part of the damage tolerance philosophy. The FASTRAN retardation model with a load sequence simulating the real operational service of an aircraft structure was used for crack growth prediction. [ABSTRACT FROM AUTHOR]

Composite and precast concrete structural systems are becoming the first choice for many construction designers. Headed fastenings are currently a relatively common technique to create joints in such types of structures. Performance of fastenings usually depends on load capacity of the concrete surrounding the fastening. The resistance of the fastening may be increased by using supplementary reinforcement designed in order to prevent concrete cone failure. The background of current design methods and experimental research is discussed in the paper. [ABSTRACT FROM AUTHOR]

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ASTM G 198, "Standard test method for determining the relative corrosion performance of driven fasteners in contact with treated wood," was accepted by consensus and published in 2011. The method has two different exposure conditions for determining fastener corrosion performance in treated wood. The first method places the wood and embedded fasteners in a chamber at 95% relative humidity (RH), 32°C, for 120 days. The second method involves a cyclic fog, with 48 h of fog followed by 72 h of dry for 120 days. The corrosion rate of embedded metals is an extremely sensitive function of the wood moisture content. While the wood moisture content is well defined, and fixed, in the constant RH test, the moisture content fluctuates and there are moisture gradients in the cyclic fog test. As a result, the fasteners in the cyclic fog test experience non-uniform and constantly changing conditions, which may be more or less challenging than the steady-state test. This paper presents the results from a combined hygrothermal/ corrosion model to explore how the moisture content and temperature at the fastener interface differs between these two methods and shows how these differences in moisture content affect corrosion. [ABSTRACT FROM AUTHOR]

This paper presents an innovative optimisation method for aircraft fuselage structural design. Detailed local finite element analyses of panel buckling are further processed such that they can be applied as failure constraints in the global level optimisation. The high computational costs involved with the finite element analyses are limited by advanced use of surrogate modelling methods. This yields high flexibility and efficiency in the local level optimisation procedure and allows for efficient gradient based search methods as well as more costly direct search optimi-sations like genetic algorithms (GAs). The method is demonstrated on a composite fuselage barrel design case considering common structural sizing variables like thicknesses and stringer dimensions. Optimised barrel designs are obtained where the constraints that are derived from the panel buckling analyses are active. The total computational cost for the complete local and global level optimisation procedures is in the order of days on common-performance hardware. [ABSTRACT FROM AUTHOR]

A test sample incorporating a painted Al alloy panel, uncoated through-hole fasteners, and scribes has recently been shown to provide an accelerated response during atmospheric corrosion testing in the field and in laboratory chambers. In this paper the galvanic current between Type 316 (UNS S31600) stainless steel (SS316) or Ti-6AI-4V (UNS R56400) fasteners and painted and scribed AA7075-T6 (UNS A97075) panels was examined during exposure in a salt fog chamber using a zero-resistance ammeter. The anodic current of the AA 7075-T6 panel and the cathodic current of each of the four fasteners were monitored using different connection schemes. The anodic current of the panel depended on the number of fasteners connected. The total cathodic current of fasteners was approximately equal to the anodic current of the AA7075-T6 panel, which validates the accuracy of the current measurement. Furthermore, galvanic interaction between the fasteners was observed such that the cathodic current of other fasteners was decreased when a new fastener was added. Scribes on a panel can interact with distant fasteners, not just the closest ones. The amount of corrosion as determined by charge and optical profilometry were close and indicated SS316 fasteners caused more corrosion attack than Ti-6Al-4V fasteners, which also is explained by differences in the cathodic current of the fasteners. [ABSTRACT FROM AUTHOR]

The hollow flange beam (HFB) is a particular cross section with two torsion rigid closed triangular flanges and a comparatively flexible web, and it is a type of high efficient cross section. This paper presents two kinds of new cold-formed flange-closed welded sections named HF1 and HF2 through change the section component and parameters of HFB. Based on the precise finite element model, nonlinear finite element method is adopted to study the static behaviors including buckling modes, deformed process, load carrying capacity and stiffness of two new kinds of section members under axial compression, bend and component axial compression-bend loads. The two new kinds of section members have some superior static behaviors including higher mean section stress and modulus of the member and have no local buckling phenomena in the elements are proofed under axial compression, and have the well characteristic of high rigidity, high ultimate capacity, local buckling of the sections always hard to occur and correlation curves replete under bend and component axial compression-bend loads, too. The new cold-formed flange-closed welded section members can go deep into the experiment study as to be used in the practical engineering. [ABSTRACT FROM AUTHOR]

In this paper, the preliminary results of the mechanical characterization in a wide range of strain rate of the 30MnB4 steel, usually adopted for fasteners, are described. In this study the different issues required to implement the dynamic test results in numerical code have been analyzed. Different experimental techniques have been used for different strain rates: universal machine, Hydro-Pneumatic Machine, JRC-Modified Hopkinson Bar and Split Hopkinson Pressure Bar. The failure at high strain rate has been examined by means of fast digital image recording systems. The material shows enhanced mechanical properties increasing the strain rate: this fact can be taken into consideration to improve the product design and the manufacturing process. The experimental research has been developed in the DynaMat laboratory of the University of Applied Sciences of Southern Switzerland and in the Laboratory of Dynamic Investigation of Materials in Nizhny Novgorod, in the frame of the Swiss -- Russian Joint Research Program. [ABSTRACT FROM AUTHOR]

In an effort to establish a theoretical outline of a criterion for preventing the vibration-induced loosening of preloaded threaded fasteners, this paper provides an experimental and analytical insight into the effect of the initial bolt preload and the excitation amplitude on the self-loosening performance of a cap screw fastener. A nonlinear model is used for predicting the clamp load loss caused by the vibration-induced loosening of cap screw fasteners under cyclic transverse loading. Experimental verification was conducted on the twisting torque variation and the effect of the preload level and transverse displacement amplitude. Comparison of the experimental and analytical results on the clamp load loss with the number of cycles verifies that the proposed model accurately predicts self-loosening performance. [ABSTRACT FROM AUTHOR]

A total of 1,533 structural bolts, consisting of four different bolt grades and six different diameters, up to 5 in. long, were tested in direct tension and shear with the threads excluded and not excluded from the shear plane. Thread lengths, tensile and shear strength, and elongation at failure were measured. The experimental values were then compared to the requirements of the current AISC, RCSC, and ASTM specifications. This paper presents and discusses the results of the experimental tests and of the subsequent comparisons. It is concluded that all fasteners tested meet the minimum strength required by ASTM and RCSC. Furthermore, it is noted that while the strength in tension and in shear with the threads excluded from the shear plane are conservatively assessed by AISC specifications, the strength with the threads not excluded from the shear plane is often not conservatively predicted. As a consequence, an alternative expression for the shear strength with the threads not excluded from the shear plane is proposed. It is also concluded that the actual thread length can be different than the nominal values, potentially affecting the available cross section in shear. Finally, the measurement of the elongation at failure shows that all grades of fastener tested have a satisfactorily ductile behavior. [ABSTRACT FROM AUTHOR]

When evaluating the strength of threaded fasteners under external loads, stress area is commonly used. However in order to elucidate the mechanical behavior of bolted joints more rigorously and extensively, it is desired to derive an analytical expression of the true cross sectional area of screw threads, with the effects of the helix and root radius taken into account. In this paper, a series of closed-form algebraic equations, which can calculate true cross sectional areas of internal and external screw threads, is derived. The equations obtained can be applied to both metric and inch screw threads with a coarse or a fine pitch. Then, the equivalent diameter of the true sectional area is defined and compared with the pitch diameter and stress area diameter. [ABSTRACT FROM AUTHOR]

The paper presents the results of an experimental study that used digital image correlation to measure the residual strains created by hole cold expansion both before and after insertion of an interference fit fastener. The study used 7075-T6 aluminium test coupons with multiple fastener holes to more closely simulate a real aircraft structure where multiple fastener holes are often cold expanded sequentially and where the interactions between the holes are a function of both the hole-to-free-edge distance as well as the pitch between the fastener holes. Both hole-to-free-edge distance and coupon thickness were varied to measure their effects on residual strain after hole cold expansion and after hole cold expansion and interference fit fastener insertion. The results showed that as the edge distance was decreased, the tensile strains at the low edge side of the coupon increased exponentially for both thick (6.35mm) and thin (1.59mm) coupons. [ABSTRACT FROM AUTHOR]

This paper presents a new strategy for the automated monitoring and classification of self-tapping threaded fastenings, based on artificial neural networks. Threaded fastenings represent one of the most common assembly methods making the automation of this task highly desirable. It has been shown that the torque versus insertion depth signature signals measured on-line can be used for monitoring threaded insertions. However, the research to date provides only a binary successful/unsuccessful type of classification. In practice when a fault occurs it is useful to know the causes leading to it. Extending earlier work by the authors, a radial basis neural network is used to classify insertion signals, differentiating successful insertions from failed insertions and categorizing different types of insertion failures. The neural network is first tested using a computer simulation study based on a mathematical model of the process. The network is then validated using experimental torque signature signals obtained from an electric screwdriver equipped with an optical shaft encoder and a rotary torque sensor. Test results are presented proving that this novel approach allows failure detection and classification in a reliable and robust way. The key advantages of the proposed method, when compared to existing methods, are improved and automated set-up procedures and its generalization capabilities in the presence of noise and component discrepancies due to tolerances. [ABSTRACT FROM AUTHOR]

Accurate determination of corrosion rates for threaded fasteners hinges on the ability to determine the surface area on which corrosion is occurring. Currently, no general analytical expression of surface area exists for the threaded fastener types. A recent voluntary withdrawal of chromated copper arsenate as the primary, long-standing preservative treatment for wood resulted in the need to determine the corrosion rates of threaded fasteners. This paper developed general analytical surface area equations for a wedge-shaped thread and the area between the threads for three cases: (1) an increasing thread root and crest diameter, (2) constant thread root and crest diameters, and (3) a constant thread root but a decreasing thread crest diameter. The expressions are applied, numerically verified, and compared to simplified models for a No. 10-2.54 cm (1 -in.) long wood screw. [ABSTRACT FROM AUTHOR]

The cold formed light-gauge profiled steel sheeting can offer considerable shear resistance acting in the steel building frame. This paper conducted the full-scale test on the shear behavior of stressed skin diaphragm using profiled sheeting connected by the self-tapping screws. A three-dimensional finite element model that simulates the stressed skin diaphragm was developed. The sheet was modeled using thin element model while the supporting members were simulated using beam elements. Fasteners were represented in the numerical model as equivalent springs. A joint test program was conducted to characterize the properties of these springs and results were reported in this study. Finite element model of the full-scale test was analyzed by use of the ANSYS package, considering nonlinearily caused by the large deflection and slip of listeners. The experimental data was compared with the results acquired by the EUR formulas and finite element analysis. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to study the loosening tendency of a threaded fastener. To achieve the objective, the threaded fastener looseness model is constructed through the following procedures. Firstly, static and dynamic threaded fastener models are derived to find the static and dynamic interior forces respectively. Secondly, for investigating the bolt loosening behaviour, the effects of thread lead angle, initial preload, vibration frequency, and the nature of material on the bolt looseness, the threaded fastener looseness model is constructed by combining the above models with a Karnopp frictional model. The proposed approach not only analyses both the static and the dynamic behaviours of the bolt as well as the bolt loosening but also detects whether the bolt is within the elastic range or not. The approach can serve as a guide for designing a thread fastening procedure to avoid the failure of threaded fasteners due to vibration. [ABSTRACT FROM AUTHOR]

On high-speed railroad lines, several dozens of standard rails have to be welded together to make a very long seamless rail. When put into service, owing to the resistance effect of the fasteners and the crossties, such a seamless rail is allowed to expand with heat and contract with cold only within 100 m of its two ends. Thus, huge longitudinal stresses may accumulate inside the rails when the temperature of the rails changes In a rail the cross-sectional area of which is 77.45 cm² and the weight of which is 60 kg per meter, 2.5 MPa of stress will be generated as the temperature of the rail changes l°C. In a hot summer, if the daily change of the temperature of the rails is 50°C, the stress in the rails will change 75 MPa. Such a large stress in the rails can cause catastrophes. Thus, a technology for the measurement of the stresses inside such a rail in service is urgently needed. The magnetoelastic wave is a physical effect caused by the sudden irreversible movement of the domain walls inside a ferromagnetic material when it is locally magnetized by an alternating magnetic field. This effect is strongly dependent upon many characteristics, such as mechanical, physical, and chemical, of the material. Based on this effect, an instrument for the measurement of the longitudinal stresses in seamless rails has been developed. Its principle and structure are introduced in this paper and a test is described. [ABSTRACT FROM AUTHOR]

This paper examines the benefits of cold expanding fastener holes at various stages of the fatigue life in a 2024-T351 low-load transfer joint. The specimens were pre-cycled to 25, 50 and 75 per cent of the baseline fatigue life of a non-expanded specimen and then cold expanded prior to cycling to final failure. The experimental test was designed to provide a close comparison with standard maintenance practices for aircraft structures and used the FALSTAFF spectrum which was derived from actual flight loading. The test results have indicated that part-life cold expansion can provide substantial improvements in fatigue life, but the actual benefit is dependent upon the degree of precycling and the length of existing cracks when the specimen is cold expanded. Additionally, tests on open hole specimens of the same material and thickness were also carried out, with attempts being made to predict the crack growth lives of these specimens. [ABSTRACT FROM AUTHOR]

Bolted flange joints are part of pressure vessel and piping components and are extensively used in the chemical, petrochemical, and nuclear power industries. They are simple structures and offer the possibility of disassembly, which makes them attractive to connect pressurized equipment and piping. In addition to being prone to leakage, they often require maintenance while in operation in which case the bolts are either retightened as in hot torquing or untightened to be replaced. Although costly shutdowns are avoided, such maintenance work exposes the operator to a potential risk because the bolt load alteration can produce a gasket load unbalance, which results in the local gasket contact stress to drop below some critical value, causing major leak and hence jeopardizing the life of the worker. This paper addresses the issue of the contact stress level unbalance around the flange when the bolts are subjected to initial tightening. The study compares the contact stress distribution variations, an analytical developed model based on the theory of rings on elastic foundation, to those given by the finite element model and the simple beam on elastic foundation model developed by Koves (2007, "Flange Joint Bolt Spacing Requirements," Proceedings of PVP2007, ASME Pressure Vessel and Piping Division Conference). This study is developed for the purpose of helping limit the degree of load increase in hot torquing or the maximum number of bolts to be replaced at a time and identify those flanges for which the bolt cannot be replaced in service. [ABSTRACT FROM AUTHOR]

This paper presents a metamodel that enables estimation of the elastic interaction that occurs in the bolted joints of a wind generator tower during the tightening sequence. In this kind of joint, there is a gap between the contact surfaces of the flanges. The metamodel is composed of four parameters, which are enough to simulate the response of the flange under the tightening loads of the bolts. Even though the behavior of the joint is nonlinear because of the gap, the parameters are obtained from two simple linear elastic analyses of a finite element (FE) model of the flange. The corresponding loss of load in the bolts has been estimated for various sequences with minimum computational cost. Thus, there is no need for costly experimental measurements or nonlinear FE simulations. [ABSTRACT FROM AUTHOR]

The poor leakage performance of flanges with full face gaskets is attributed to the low reliability of the existing design methods, and in particular, their lack of assessing accurately the bolt and gasket load changes. The prediction of tightness of bolted joints relies very much on the level of precision of the gasket contact stress during operation. The accurate evaluation of this stress requires a flexibility analysis of the joint that includes the flange, gasket, and bolts, and the interaction between them. This paper analyzes the distribution of gasket stress and the load change in bolted joints with full face gaskets. It proposes a simple analytical approach capable of predicting flange rotation and bolt load change during operation. The method is based on the gasket-bolt-flange elastic interaction, including flange rotational flexibility. The proposed model is supported by comparison with numerical finite element analysis of different size flanges. [ABSTRACT FROM AUTHOR]

Design rules for flat face flanges with metal-to-metal contact beyond the bolt circle are covered by Appendix Y of the American Society of Mechanical Engineers Code. These design rules are based on Schneider's work (1968, "Flat Faces Flanges With Metal-to-Metal Contact Beyond the Bolt Circle," ASME J. Eng. Power, 90(1), pp. 82-88). The prediction of tightness of these bolted joints relies very much on the level of precision of the self-sealing gasket compression during operation. The evaluation of this compression requires a rigorous flexibility analysis of the joint including bolt-flange elastic interaction. This paper analyses flange separation and the bolt load change in flat face bolted joints. It proposes two different analytical approaches capable of predicting flange rotation and bolt load change during operation. The first method is based on the beam theory applied to a continuous flange sector. This approach is an improvement of the discrete beam theory used in the Schneider model. The second method is based on the circular plate theory and is developed for the purpose of a more accurate assessment of the load changes. As in the Taylor Forge method, this approach is, in general, better suited than the beam theory for flat face flanges, in particular when the flange width is small. The proposed models are compared with the discrete beam theory and validated using numerical finite element analysis on different flange sizes. [ABSTRACT FROM AUTHOR]